1. Field of the Invention
This invention relates to a process for preparing poly{[benzo(1,2-d:5,4-d')bisthiazole-2,6-diyl]-1,4-phenylene}. In a further aspect, this invention relates to a process for preparing 4,6-diaminobenzene-1,3-dithiol.
2. Description of the Prior Art
Various procedures are known in the art for preparing poly {[benzo(1,2-d:4,5-d')bisthiazole-2,6-diyl]-1,4-phenylene} and its cis isomer in order to form shaped articles. For example, in U.S. Pat. No. 4,225,700, the trans isomer is prepared by reacting 2,5-diamino-1,4-benzenedithiol dihydrochloride with terephthalic acid in polyphosphoric acid. The polymerization mixture is precipitated into water and successively washed with water, dilute ammonium hydroxide and then water. Alternatively, the mixture is combined with methanesulfonic acid, precipitated into methanol and successively washed with water, aqueous ammonium hydroxide and methanol and then freeze dried from benzene.
In U.S. Pat. No. 4,051,108, the cis isomer as well as other para ordered aromatic heterocyclic polymers are formed into films and coatings from a dispersion of particles of the polymer. The patent, however, does not set forth a process for preparing the cis isomer. A similar technique is described in U.S. Pat. No. 3,987,015.
In U.S. Pat. No. 3,681,297, related but distinct polybenzothiazoles are prepared by reacting a selected dialdehyde with a defined aromatic bismercaptoamine to obtain a polybenzothiazoline. This material is then subjected to oxidation to obtain the related polybenzothiazole. In the event that unconverted reactants remain, the patent discloses that the polymer may be heated in excess of 175.degree. C., preferably in the range of 250-400.degree. C. in nitrogen or 250.degree.-350.degree. C. in air to cause chain extending polymerization.
Imai et al, "Polybenzazoles," Makromolekulare chimi, Vol. 83, July, 1964, pages 179-187, discloses the self condensation of amino-benzoic acid compounds to form high molecular weight polybenzazoles. In the introduction of the art, reactions of di-substituted benzidines with dicarboxylic acids are described.
In Likhosherstov et al, J. Gen Chem. U.S.S.R., 3, 183 (1933) described in Chem. Abst. 28: 1677 (1934), refers to the use of the reaction product of dichlorourea and ammonium cyanate with m-phenylenediamine to afford the dithiocyano compound.
In Grandolini et al, Gazz. Chim. Ital., 89, 2543 (1959), dithiocyanates can be made to cyclyze on treatment with acid.
In the publication to V. K. Schwabe and J. Voight entitled "Zur Reduktion organischer Rhodenverbindungen an Quecksilberkathoden in Z. Elektrochem., 56, 44 (1952), aromatic thiocyanates are electrochemically reduced to the corresponding thiol.
In application Ser. No. 483,799 filed on Apr. 11, 1983 in the name of Edward C. Chenevey, entitled "Process for Heat Treating Shaped Articles of Poly{[benzo[1,2-d:4,5-d') bisthiazole-2,6-diyl]-1,4-phenylene}, Its Cis Isomer or Mixtures Thereof and the Articles Formed Thereby" and assigned to the assignee of the present application, there is described a process for simultaneously heating and stretching shaped articles of the defined polymer.
In application Ser. No. 483,797 filed on Apr. 11, 1983, now U.S. Pat. No. 4,487,735, in the names of Edward C. Chenevey and Ronald Kafchinski, entitled "Process for Preparing Film of Poly{[benzo(1,2-d:4,5-d') bisthiazole-2,6-diyl]-1,4-phenylene}, Its Cis Isomer or Mixtures Thereof", assigned to the assignee of the present application now U.S. Pat. No. 4,487,735, there is described a process for preparing film of the polymer by extruding it on a casting roll, subjecting it to elevated temperatures and, preferably, heat treating it under tension.
In application Ser. No. 483,798 filed on Apr. 11, 1983, in the names of Edward C. Chenevey and Thaddeus E. Helminiak, entitled "Process for Preparing Shaped Articles of Rigid Rod Heterocyclic Liquid Crystalline Polymers" and assigned to the assignee of the present application, there is described a process for preparing shaped articles of polymers such as poly{[benzo(1,2-d:4,5-d')bisthiazole-2,6-diyl]-1,4-phenylene} by polymerizing the reactants in a reaction medium and directly forming the shaped articles therefrom.
In application Ser. No. 542,831 filed in the name of Edward C. Chenevey, entitled "Process for Preparing Shaped Articles of Poly{[benzo(1,2-d:4,5-d')bisthiazole-2,6-diyl]-1,4-phenylene}, Its Cis Isomer or Mixtures Thereof from a Dope Containing Concentrated Sulfuric Acid" and assigned to the assignee of the present application, the cis isomer and/or the trans isomer is dissolved into concentrated sulfuric acid and the resulting dope is used to form shaped articles.